The present invention relates to the art of power driven threading machines, and more particularly to a nipple chuck for holding a threaded end of a pipe nipple workpiece in a power driven pipe threading machine while an unthreaded end of the nipple is threaded.
It is of course well known that power driven pipe threading machines are used to cut, bevel and/or thread one or both ends of a length of pipe. Such pipe threading machines comprise a spindle through which a length of pipe can extend, a chuck assembly for gripping and rotating the pipe, and tools for cutting, reaming and/or threading an end of the pipe as it is rotated
The chuck assembly includes a machine chuck mounted on the spindle for rotation therewith and which chuck includes an axial passage through which the workpiece extends from the spindle to the cutting tools. A number of chuck jaws, usually three, are carried on the machine chuck and are shiftable radially of the spindle axis between an operating position firmly gripping the pipe and an open position releasing the pipe.
The cutting tools are generally mounted on the threading machine so as to be movable into and out of operating positions relative to the workpiece, and the thread cutting tool generally is in the form of a die head supporting threading dies and shiftable along the working axis of the machine to accommodate different pipe lengths.
In connection with producing pipe nipples which are short pieces of pipe threaded at both ends, a length of pipe is first fed from the rear of the machine through the spindle and chuck assembly to advance the pipe into a working position relative to the cutting tools. The machine chuck jaws are then securely engaged with the pipe, the machine chuck is rotated by the power driven spindle, and short pipe sections are successively threaded at one end and then cut as the pipe is intermittently advanced through the machine. These short pipe sections are then threaded at the other ends thereof to produce pipe nipples and, in connection with such threading, a nipple chuck is required to firmly grip the previously threaded end to enable rotation of the workpiece without deforming the previously cut threads.
Nipple chucks are well known and heretofore have included a wide variety of structures generally in the form of radially displaceable collet sections having internal threads matching the externally threaded pipe nipple. Further, such previous nipple chucks have included a rigid shaft or the like on which the collet sections are mounted and by which the nipple chuck is held in the machine chuck jaws, and radially or axially displaceable cams are employed to displace the collet sections against the pipe nipple. Prior nipple chucks of the foregoing character are disadvantageous for a number of reasons. In this respect, they are heavy, structurally complex assemblies which are cumbersome to use in that the mounting shaft has to be introduced into the machine chuck jaws, and then another separate camming component or the like has to be actuated to displace the collet sections radially onto the pipe nipple workpiece. The camming component has to be manually shifted to displace the collet sections and, often, a locking mechanism is required to hold the camming component firmly in place during operation of the machine. It will be appreciated, therefore, that such nipple chucks require several accurately machined moving parts, and such parts are not only very expensive to manufacture and assemble, but result in an assembly in which the parts are prone to become misaligned and to jamming during use. The presence of metal scrap in connection with operating a pipe threading machine introduces a further problem with respect to interfering with the relative movement between component parts of such nipple chucks.
Other known nipple chucks include internally threaded unitary chucks which have no moving parts but which require the operator to manually screw each pipe nipple into the chuck threads, and then to manually unscrew the nipple therefrom following the threading operation. This unduly time consuming operation consumes the operator's time and thus adds to the expense of the threading operation. Also, scrap metal particles will inevitably be deposited within the threaded interior of the chuck causing binding between the threads of the chuck and the nipple. Binding also often occurs in such unitary chucks as a result of the nipple being screwed into the chuck during the threading operation. It will be appreciated that any such binding not only encumbers separation of the nipple from the chuck but also subjects the operator to potential injury in connection with such separation should, for example, his hand slip on the threaded end of the nipple which has to be grasped and manually turned to remove the nipple from the chuck.